Fixed wireless systems are currently employed for local telecommunication networks, such as fixed radio access. Known systems comprise an antenna and decoding means which are located, for instance adjacent a telephone. The antenna receives the signal and provides a further signal by wire to a decoding means. Thus subscribers are connected to a telecommunications network by a radio link in place of the more traditional method of copper cable. Such wireless local loop systems will be capable of delivering a wide range of access services from POTS, ISDN to broadband data. The radio transceivers at the subscribers premises communicate with a base station, which provides cellular coverage over, for example, a 5 km radius in urban environments. A typical base station will support 500-2000 subscribers. Each base station is connected to the standard PSTN switch via a conventional transmission link/network.
When a wireless local loop telecommunications system is originally deployed, then a base station of a particular capacity will be installed to cover a particular area. The capabilities of the base station will be commensurate with the anticipated coverage and capacity requirement. Subscribers antennas will be mounted outside, for instance on a chimney and upon installation will be directed towards the nearest base station or repeater antenna (any future reference to a base station shall be taken to include a repeater). A potential problem with this sort of alignment is that, for instance, the antenna is aligned during the winter months but by the following summer, foliage of a growing tree has obscured the line of sight. Alternatively a building may have been erected in the line of sight. As more subscribers are acquired, more base stations may be deployed in order to increase capacity, thereby requiring the realignment of some subscriber antennas. There is also becoming an increasing interest in receive-only broad band access systems such as multi-point video distribution system MVDS and problems similar to wireless local loop have been found to occur.